Production of Ihpf Components Having a Flange

ABSTRACT

The present invention relates to a method of producing a hollow profile which has at least one flange by internal high pressure forming. During the internal high pressure forming, the dimensions and the position of the flange are not changed relative to the finished hollow profile then formed.

BACKGROUND AND SUMMARY OF THE INVENTION

This invention relates to a method of producing a hollow profile havingat least one flange by means of internal high pressure forming.

Conventional hollow profiles with flanges are generally produced byextrusion. In automobile construction, the flange is required in orderto fasten the hollow profile, produced by extrusion for example, tofurther vehicle body parts.

German document DE 10130794 A1, for example, discloses an extrudedprofile which has a flange and is subsequently subjected to internalhigh pressure forming, the course and the direction of the flange overthe length of the structural part not being established in adimensionally accurate manner until during deformation according to theinternal high pressure process.

However, an extruded hollow profile having a flange generally has thedisadvantage that the hollow profile can only be bent and/or widenedwith difficulty. The reason for this is that the connecting point of theflange on the hollow profile acts like a tension rod against the formingforce. In addition, on account of the accumulation of material at thisconnecting point, the flange cannot expand sufficiently and thereforethe hollow profile cannot be formed in a controlled manner.

It is known from German document DE 19905365 A1 to produce a hollowprofile having a flange by roll forming from a sheet-metal blank. Thehollow profile is then subsequently subjected to internal high pressureforming. In this case, the flange is established beforehand in such away that its position and dimensions are not formed until during theinternal high pressure forming. However, such a method is complicated inits implementation inasmuch as that portion of the flange on the initialhollow profile which is to be deformed during the internal high pressureforming has to be accurately established or calculated as a function ofthe holding-down force for the flange on the one hand and the internalhigh pressure to be applied on the other hand. In addition, the hollowprofile shown in this publication has the disadvantage that the initialhollow profile has sharp edges, which, on account of the pronouncedhardening during the profile production process, can remain behind asvisible residual edges or undulations on the final finished hollowprofile produced by the IHPF process. The bending-back or stretching ofsuch profile edges, hardened to a pronounced extent, cannot becompletely taken into account in the IHPF process.

Starting therefrom, the object of the present invention is to provide amethod of producing a hollow profile by means of which a hollow profilehaving at least one flange can be produced in a simple and controlledmanner.

This object is achieved by a method having the features claimed.

The method is distinguished by the fact that an initial hollow profileconsists of a single sheet, at least one flange being formed in thelongitudinal direction of the initial hollow profile likewise bycorresponding folding or roll forming of the sheet. The sheet can beproduced in particular from a sheet-metal blank and/or a roll-formedsheet unwound from the coil.

Then, in order to form a closed initial hollow profile, the jointlocation of the sheet is welded and the closed initial hollow profile isinserted into an internal high pressure forming (IHPF) tool. During theinsertion, the at least one flange is positioned in a correspondingcavity in the IHPF tool and is clamped in place with a definedholding-down force during the internal high pressure forming.

According to the invention, the inner contour of the IHPF tool, on theone hand, and the holding-down force to be applied on the flange duringthe internal high pressure forming, on the other hand, are selected insuch a way that the position of the flange always remains unchangedrelative to the finished hollow profile then formed.

In this case, it is possible according to the invention to establish theholding-down force in such an order of magnitude that a subsequent flowof material into the finished hollow profile on no account occurs duringthe internal high pressure forming.

Under certain circumstances, however, it may also be desired for such asubsequent flow of material from the flange into the finished hollowprofile to be allowed, so that a corresponding holding-down force is tobe selected.

According to the invention, the flange can be produced in different waysduring the folding or roll forming of the sheet.

Thus it is possible for the flange to be formed by doubling of thematerial of the sheet during the folding or roll forming, that is to saythe sheet is folded over or roll-formed, with the flange being formed.

Another possibility is to fold or roll-form the sheet in such a way thatthe two ends of the sheet form an overlapping joint for forming theflange.

However, it is also possible for the sheet to be folded or roll-formedat one end, with the flange being formed, and for the other end, duringthe folding or roll-forming, to be formed in such a way that it abutsagainst the transition region between the flange and the initial hollowprofile.

In order to form a closed initial hollow profile, the sheet is weldedtogether in the region of its free ends. Since these free ends can liein the region of the flange or outside this region, welding is carriedout there in each case.

If a subsequent flow of material from the flange is desired during theinternal high pressure forming, the weld is at any rate located outsidethe flange region in the initial hollow profile.

Hollow profiles produced by the method according to the invention aresuitable, for example, for use in body construction as roof frames, sidesills, transverse members or longitudinal and transverse members in thebody floor assembly, in which case the adjacent body components can thenbe attached to the flange by conventional joining processes, such asresistance spot welding for example.

Further advantages and features of the method according to the inventionfollow from the description below with reference to the attacheddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows an IHPF tool with a flange clamped in place;

FIGS. 2 a and 2 b show an initial hollow profile with differentpositions of the weld;

FIG. 3 shows a further initial hollow profile with a single flange; and

FIGS. 4 a and 4 b respectively show an initial hollow profile with aweld outside the flange region.

DETAILED DESCRIPTION OF THE INVENTION

Shown schematically in FIG. 1 is an IHPF tool 1 which consists of a toppart 2 and a bottom part 3. Both parts 2 and 3 form a cavity 4, whichcorresponds to the contour of the final finished hollow profile.

A sheet-metal blank formed into an initial hollow profile 5 is insertedinto this cavity 4. The initial hollow profile 5 has a flange 6, whichis clamped in place in a corresponding section 7 of the cavity 4.

The clamping in place can be effected with such a holding-down forcethat either no subsequent flow of material can take place from theregion of the flange 6 into the finished hollow profile or such asubsequent flow of material is allowed.

By way of example, FIGS. 2 a and 2 b show an initial hollow profile 5 inwhich a flange 8 is formed by an overlapping joint of the free ends ofthe sheet. The flange 8 can then be welded either by a weld 9 beingprovided in the joint region of the flange 8 (FIG. 2 a) or by a weld 9being provided in the course of the flange 8 transversely to the latter(FIG. 2 b).

Furthermore, by way of example, FIG. 3 shows an initial hollow profile 5in which the flange 10 is formed by a free end of the sheet beingappropriately bent over and by the other free end being welded on in thetransition region between the flange 10 and the initial hollow profile5.

A further possibility consists in forming a flange 11 of the initialhollow profile 5 in such a way that the sheet is folded over and thusoverlaps in the region provided for the flange 11. This is shown by wayof example in FIG. 4 a for a single flange 11 and in FIG. 4 b for twoflanges 11. In both cases the weld 9 is located outside the flange inthe region of the initial hollow profile 5. Such an initial hollowprofile with a weld 9 established outside the flange region ispreferably to be used when a subsequent flow of material from the regionof the flange 11 during the internal high pressure forming is to bepermitted.

1-3. (canceled)
 4. A method of producing a hollow profile having atleast one flange extending along the hollow profile, comprising: foldingor roll forming an initial hollow profile from a sheet, with at leastone flange being formed so as to project from the initial hollow profileby doubling the material of the sheet; welding a joint location of theinitial hollow profile outside a region of the flange; and internal highpressure forming the initial hollow profile into a finished hollowprofile by applying an internal high pressure by means of a fluid intothe interior of the initial hollow profile, with the at least one flangebeing clamped in place in an IHPF tool in such a way that its positionand dimensions remain unchanged relative to the finished hollow profile.5. The method as claimed in claim 4, wherein the at least one flange,when the IHPF tool is closed, is acted upon by a holding-down forcewhich prevents a subsequent flow of material from the flange into thefinished hollow profile during internal high pressure forming.
 6. Themethod as claimed in claim 4, wherein the at least one flange, when theIHPF tool is closed, is acted upon by a holding-down force which allowsa defined subsequent flow of material from the flange into the finishedhollow profile during internal high pressure forming.